The Department of Homeland Security is under more pressure than ever to dump private prisons for immigrant detainees

A detainee at US Immigration and Customs Enforcement's Stewart Detention Center in Lumpkin, Georgia, leaves the cafeteria to go back to the living units. Associated Press/Kate Brumback

A growing group of prison-reform advocates and lawmakers, including Vermont Sen. Bernie Sanders, are now urging the US Department of Homeland Security (DHS) to cease its use of private prisons for undocumented immigrants.

The DOJ's move was hailed by some as a progressive step toward national prison reform, but criticized by others for not going far enough. Just 22,000 of the country's 2 million prisoners are federal inmates housed in private prisons.

Meanwhile, US immigration authorities use private prisons to house 62% of the roughly 400,000 people detained each year by US Immigration and Customs Enforcement (ICE).

On Monday, Sanders issued a joint letter with Democratic Rep. Raul M. Grijalva of Arizona, calling on Homeland Security Secretary Jeh Johnson to phase out contracts with for-profit prison companies by declining to renew them or reducing their scope.

"Given the impact on detainees, the high cost to taxpayers and the Department of Justice's recent decision, we believe the Department of Homeland Security can and should immediately begin phasing out for-profit, privately run immigration detention facilities," the letter read.

They're not the only ones to issue a public call on the DHS to end its use of private prisons. The New York Times ran an editorial on Monday calling the ICE detention facilities a "national shame" with "hellish conditions," urging the department to follow in the DOJ's footsteps.

"They are notoriously violent and dysfunctional, operating even more opaquely than state-run facilities, while paying miserable wages," the editorial read.

Privately run ICE facilities have long been under scrutiny from organizations like the American Civil Liberties Union (ACLU), which in a 2014 report documented "dangerous, squalid, and tense conditions" in the detention centers.

According to the ACLU's investigation, detainees across the five facilities it examined were subject to conditions of overcrowding and extreme isolation, as well as insufficient medical care and lack of family contact.

In a statement last week, Carl Takei of the ACLU's National Prison Project slammed ICE for ignoring criticisms of its for-profit contractors and continuing to renew contracts with private companies.

"Now that the Justice Department has firmly declared its own private prison experiment to be a failure, any attempt by ICE to defend its continued relationships with these companies will ring hollow," Takei said.

Private-prison companies like the GEO Group and Corrections Corp. of America have been shifting their strategy for some time toward ICE facilities, according to Christopher Petrella, a lecturer at Bates College and member of Grassroots Leadership, an advocacy group that studies private prisons.

"They've been lobbying the Department of Homeland Security, in particular, very heavily," Petrella told Business Insider. "ICE is the growth sector — and I am loath to use that language because we're talking about human beings here. But from ICE and GEO's perspective, that's the discourse that they use."

ICE did not comment on Sanders and Grijalva's letter, but referred Business Insider to a statement issued last week.

"US Immigration and Customs Enforcement (ICE) remains committed to providing a safe and humane environment for all those in its custody," spokeswoman Jennifer Elzea said in the statement.